A data bus system transfers words and word portions on a data bus between master devices and slave devices. A size bus carries a size code in fixed-byte format that identifies a number of bytes being transferred in one or more words and/or word portions of a transaction. A byte-enable bus carries a byte-enable code that identifies valid bytes of a word. An interface decodes the byte-enable codes to size codes and, where an odd-byte byte-enable code is decoded, it decodes the odd-byte byte-enable code to a plurality of size codes.
Presented herein are systems and methods for two address map for transactions between an X-bit processor and a Y-bit wide memory. A processor subsystem comprises a first address space, a second address space, and a bridge. The first address space stores data words of a first length. The second address space stores data words of a second length. The bridge performs one transaction after receiving a transaction with an address corresponding to the first address space and performs two transactions after receiving a transaction with the address corresponding to the second address space.
A method and an apparatus in a computer system for connecting buses with different clock frequencies are provided. The method comprises receiving a request transmitted from a master to a slave. If the clock frequency of the master is lower than that of the slave such that the slave sees more requests than the master does, redundant cycles of the request signal are masked lest the slave repeatedly receive the request. The request is then transferred to the slave. If the clock frequency of the master is higher than that of the slave such that the slave cannot receive the request in time, then the request signal is lengthened so that the request signal is synchronized with the clock cycles of the slave. The output data responded from the slave is then transferred to the master.
A bus system, such as an internal bus system located within a digital device, is disclosed herein. The bus system comprises a plurality of master buses, each master bus connected to at least one master. The bus system also comprises a multi-bus interface connected to the plurality of master buses and a slave bus connected to the multi-bus interface. The multi-bus interface enables one master bus at a time to access the slave bus. Also disclosed herein are bus structures and methods for interfacing between master buses and slave buses.